1. Field of the Invention
The present general inventive concept relates to a piezoelectric inkjet head, and more particularly, to a piezoelectric inkjet head having a membrane to prevent cross-talk, and a method of manufacturing the same.
2. Description of the Related Art
An inkjet head is a device for printing a predetermined color image by ejecting minute droplets of ink on desired areas of a printing medium. Inkjet heads are nowadays also used in flat panel displays such as liquid crystal displays (LCDs), organic light emitting diodes (OLEDs), plasma display panels (PDPs), and printed circuit boards including metal wirings and resistances, and semiconductor packaging.
Inkjet heads can be generally classified into two types according to the method of ejecting ink droplets. One type is a thermal inkjet head that ejects ink droplets using the expansion force of ink bubbles created using a heat source, and the other type is a piezoelectric inkjet head that ejects inkjet droplets using a pressure created by the deformation of a piezoelectric element.
FIG. 1 is an exploded perspective view of a conventional piezoelectric inkjet head which has been disclosed in Korean Patent Publication No. 2003-0050477 (U.S. Patent Publication No. 2003-0112300) by the applicant of the present general inventive concept.
Referring to FIG. 1, the conventional piezoelectric inkjet head has a structure in which three silicon substrates 30, 40, and 50 are stacked and combined. Of the three silicon substrates 30, 40, and 50, the upper substrate 30 has a plurality of pressure chambers 32 having a predetermined depth on a lower surface thereof. An ink inlet 31 connected to an ink storage (not shown) is formed through the upper substrate 30. The pressure chambers 32 are arranged in two rows on both sides of a manifold 41 formed in the middle substrate 40. A plurality of piezoelectric actuators 60 that provide a driving force to eject ink to each of the pressure chambers 32 are formed on an upper surface of the upper substrate 30. The middle substrate 40 includes a manifold 41 connected to the ink inlet 31, and a plurality of restrictors 42 respectively connected to each of the pressure chambers 32 are formed on the both sides of the manifold 41. Also, the middle substrate 40 includes a plurality of first dampers 43 perpendicularly formed through the middle substrate 40 on positions corresponding to each of the pressure chambers 32. A plurality of second dampers 53 connected to the first dampers 43 are formed in upper part of the lower substrate 50, and a plurality of nozzles 51 connected to the second dampers 53 are formed in a lower part of the lower substrate 50.
However, in the conventional piezoelectric inkjet head having the above structure, when the pressure of each of the pressure chambers 32 is increased by the driving of the piezoelectric actuators 60, the ink in the pressure chambers 32 is ejected to the outside through the nozzles 51, and at the same time, backflows towards the manifold 41 through the restrictors 42. Due to the backflow of ink, the pressure in the manifold 41 becomes non-uniform, and a pressure change in the manifold 41 affects to the adjacent pressure chambers 32, that is, cross-talk occurs. The cross-talk causes unstable meniscus of ink in the nozzles 51 connected to the adjacent pressure chambers 32, and thus, causes variations of the speed and volume of ink droplets ejected through each of the nozzles 51.